In recent years, for acquiring high luminance in color image display apparatuses, white sub-pixels for displaying a white color, for example, are added in addition to three types of sub-pixels, that is, red sub-pixels for displaying a red color, green sub-pixels for displaying a green color, and blue sub-pixels for displaying a blue color.
In the color image display apparatus including white sub-pixels, while bright display is possible in the case of an achromatic color or colors in the vicinity thereof, display becomes relatively dark in the case of displaying colors of high chroma. In other words, a displayable color range becomes narrower as brightness increases.
In contrast, for video signals acquired by a camera or the like, a maximum value is normally set irrespective of the chroma. Therefore, when an image is to be displayed on the color image display apparatus including white sub-pixels based on such video signals, the part that should be displayed brightly with high chroma is displayed with chroma and brightness that are relatively lowered.
For improving such a display state, for example, Japanese Patent Application Laid-open No. 2009-520241 (Patent Document 1) discloses a technique of uniformly decreasing chroma of video signals to compensate for lowering of brightness.
Patent Document 1: Japanese Patent Application Laid-open No. 2009-520241